Rating System

LEED BD+C: New Construction

Rating System Version

v2 - LEED 2.2

Inquiry

Our project is the renovation of an historic building on the north half of a downtown urban block. The existing building is a masonry structure approximately two-stories high with a vaulted roof. The property owner transferred the site\'s Floor Area Ratio (FAR) allowance to the owner of the half block property directly to south and a developer constructed a high-rise condominium tower on that site, using the added height allowance. The same developer constructed a high-rise apartment tower on the block immediately to the west. The roofs on both towers meet the reflectance and emittance criteria of SS c7.2. The design team conducted a site shading study using a massing model of the site vicinity on a heliodon. The study showed that the roof of the historic building will be 100% shaded from September through April, from approximately 8:00 AM until sunset. Even on June 21, the roof will be shaded more than 50% from approximately 9:00 AM until sunset. On average, from May through August the roof will be more than 75% shaded. Additionally, approximately 90% of the vaulted roof has a slope greater than 2:12, especially on the small, non-shaded roof area that slopes to the north. The roof that will be installed meets the Energy Star solar reflectance criteria. However, thermal emittance was measured at 0.9 when tested in accordance with ASTM C 1371, which is not the test referenced by LEED, ASTM E408-71. Several LEED Certified projects have achieved Sustainable Sites Credit 7.1 by demonstrating shading of non-roof impervious surfaces provided by adjacent buildings along with other strategies listed in the credit requirements. We feel that the same should apply to shading of roofs. A roof will not contribute to the heat island effect, regardless of its reflectance and emittance, if it is primarily in shade. Also, the owner of this building took action in transferring the site\'s FAR allowance to the property to the south, which allowed the neighboring building to achieve a height that provides significant shade. Do you agree that this project meets the intent of this credit, to reduce heat islands, and will achieve this credit?